Tuning device with stop mechanism



June 5, 1945. H. C. HALL 2,377,790,

TUNING DEVICE WITH STOP MECHANISM Filed March 19, 1942 I III v nll r 34 INVEN TOR Harry 0 17!) m'vcwm HTIU FNEYS siderable variation may be Patented June 5, 1945 2,377,790 TUNING DEVICE WITH STOP MECHANISM Harry C. Hall. Indianapolis,

Ind.. assignor to P. R. Mallory & 00., Inc., Indianapolis, Ind;, a. corporation of Delaware Application March 19, 1942, Serial No. 435,331

3 Claims.

This invention relates to inductance devices of the continuously variable slide-wire type and to the stop mechanism therefor.

An object of the invention is to improve slidewire variable inductance mechanism therefor.

Other objects of the invention will be apparent from the following description and accompanying drawing taken in connection with the appended claims.

The invention struction,

in the drawing.

In the drawing: Figure 1 is a side elevation, partly in section of a slide-wire inductance device embodying features of the present invention;

slides on the wire of the coil as the coil is rotated.

While a preferred embodiment of the-invention is described herein, it; is contemplated that conmade in the method of procedure and the construction of parts without departing from the spirit of the invention. In

the following description and in the claims, parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts as the art will permit.

Referring to the drawing, the slide-wire variable inductance, deviceshown in Figures 1 and 2 comprises a pair of spaced parallel end plates ill I and H held in spaced, parallel relation by longitudinal spacer rods l3. The unit is enclosed in a metal can shield l4 and may be mounted in the apparatus in which it is to be used by a flanged mounting base l5 welded to the outside of the ihield. A rotatable control shaft l6 extends axi- Figure 2 is a section on the line 2-2 of Fig- Sliding contact 3| rod 30 to afford a sliding contact for varying the ally through the shield and is pivoted in end plates in and H for rotation by control knob ll. 7

The shaft carries a coil form l8 of tubular insulating material such as resin impregnated fibre.

Bare wire coil I 9 is wound on the surface of form l8 with adjacent turns spaced from each other. If desired, the form may be provided with a shallow groove in which the wire 19 is held against displacement. Metal caps 20 and 2| are attached over the ends of the coil form and have cylindrical flanges thereon which overlie the cylindrical surface of form and are provided at their edges with upturned stop lugs 22 and 23. The ends of coil l9 are connected to these lugs. End cap has a central aperture spacing and insulating it from shaft I 6. A fork-shaped contact spring 24 is mounted on a suitable insulating block 25 inside end wall I0 and carries a pair of contact brushes 26 on the ends of its fork arms which slide on cap 20. thereby providing a slip ring connection to the tact spring 24 extends out through a suitable aperture in the shield M to provide an external circuit connection. End cap 2| is positively grounded to the frame of the device by contact spring 21 secured to end wall II and carrying contact brushes 28 sliding against cap 2|. Mounting base [5 is provided with a punched down grounding lug.

Parallel rods 29 and 30 extend along the side of coil form I 8 and are supported at their ends by end walls l0 and II. Guide rod 29 is disposed outside of trolley rod 30 in the same radial plane. engages coil l9 and trolley amount of coil l9 in the electric circuit. Contact 3| comprises a stamping formed from sheet spring metal having its central body portion bent to form a channel across the middle of the contact which slides on rod 30 and having grooved contact nibs at its ends riding on the 'wire of coil is.

The stop member 32, formed of Bakelite, ceramic or other molded on guide rod 29, and has flanges engaging the sides of trolley rod 30 at both edges of contact 3|. As contact 3| is moved along rod 30 it moves stop member 32 along with it. Member 32 is thus brought into position to engage stop lugs 22 and 23 and stop the rotation of the coil when the contact approaches the ends of its path of travel.

The preferred shape of stop member 32 is shown in Figures 4 and 5. It is formed of a single molded piece of insulating material having a generally end of the coil. Con-' insulating material rides 2 2,377,790 V-shaped contour and having a hole 35 near the and rotationless displacement along said rod, said apex of the V for slidably embracing shaft 29. stop member having parts protruding into the The legs of the V member are connected at their edges for part of their length by flanges or webs 36 and 31. These flanges have notches 38 and 39, respectively, in their edges. When the stop member is mounted in the tuning device the notches 38 and 39 flt over rod 30 to prevent member 32 from rotating. The inside of flanges 35 and 31 engage the edges of contact 3| so that the contact moves stop member 32 along with it. The arms of the stop member have reinforcing ridges along their inside faces which are terminated in square ends 33 and 34 which act as the stop surfaces whichencounter stop lugs 22 and 23 of the rotating coil at the ends of the contact travel.

In operation, when the coil is rotated the grooved nibs of contact 3| slide along the wire l9 and hence slide the contact element 3| along rod 30. Contact element 3| slides stop member 32 along with it. If the coil is rotated sufilciently to bring contact element 3| near to the end of the coil, the leading stop surface 33 or 34 on member 32 will engage stop lug 22 or 23 to prevent further rotation of the coil.

This arrangement permits substantially the entire length of coil H to be traversed by contact 3| but efiectively stops the rotation of the coil just before the leading nib of the contact reaches the end of the coil thus protecting the contact from damage and preventing it from over-running the end of the coil. The stop mechanism will withstand severe use and vibration and does not readily get out of order or require adjustment.

While the present invention, as to its objects and advantages, has been described herein as carried out in specific embodiments thereof, it is not desired to be limited thereby but it is intended to cover the invention broadly within the spirit and scope of the appended claims.

What is claimed is: y

1. In a variable inductance devic wherein a bare helical conductive coil is mounted for retation about itslongitudinal axis, a trolley rod is mounted in parallel-spaced position along said coil, and a contact member is mounted in sliding contact with said rod and the conductor of said coil and is guided along said rod and said conductor solely by rotation of said coil, the improvement which comprises stop projections on the ends of the circumferential surface of said coil and rotating therewith, and a stop member engaged by said contact member for joint sliding path of said step projections for abutting against the same and for directly and positively locking the coil against further rotation when said stop and contact members reach the ends of said coil.

2. A variable inductance device comprising in combination a bare helical conductive coil, a trolley rod parallel-spaced to the side of the coil, means for supporting said coil and said rod for relative rotational displacement with respect to each other; a contact member mounted in contact with said rod and said coil and having guides for guiding itselfalong said rod and the conductor of said coil during the said rotational displacement, stop projections on the ends of the circumferential surface of said coil and rotating therewith, and a stop member engaged y said contact member for joint sliding and rotationless displacement along said rod, said member having parts protruding in a generally tangential direction into the path of said step projections for abutting against the same and for directly and positively locking the coil and the rod against further relative rotation when said stop and contact members reach the ends of said coil.

3. A slide-wire variable inductance device comprising in combination a coil unit constituted of a circular form and of an inductive coil of bare wire wound thereon mounted for rotation about a longitudinal axis, a trolley rod mounted in parallel-spaced relation with respect to the side of said coil, a resilient contact member biased to be held by its compliance in an interposed position between said coil unit and said trolley rod, said contact member having surfaces slideably engaging said wire and said rod and guiding the same along said rod when said coil unit is rotated, a stop projection on the circumferential surface of said coil unit at each end thereof and rotating with said unit, a stop member straddling said contact member and slideable therewith along said trolley rod having arms extending in substantially tangential direction towards the circumference of said coil unit, and a stop face on each of said arms protruding into the rotary path of said stop projections and adapted to be engaged by such projections when said contact and stop members approach the ends of said coil thereby directly and positively locking the coil unit against further rotation.

HARRY C. HALL. 

